Laminated static charge suppressor and method of making same

ABSTRACT

A laminated static charge suppressing bus which is composed of a strip of insulating material to which a conducting strip and a plurality of ionizing elements are mounted. The conducting strip is mounted on one side of the insulating strip and the plurality of ionizing elements are mounted serially along the other side of the insulating strip directly opposite the conducting strip. The ionizing elements are capacitively coupled to the conducting strip and contain pointed emitting tips extending beyond the edge of the insulating strip. When the ionizing elements are excited, the emitting tips establish a corona discharge in gas around the tips for removing static charges from paper, plastic webs and sheetlike textile materials.

United States Patent Iosue et al.

1451 Mar. 28, 1972 [72] Inventors: Michael F. losue, Danielson; RobertE.

Sanders, Saybrook, both of Conn.

[73] Assignee: Rogers Corporation, Rogers, Conn. 221 Filed: Se t, 9,1970 [21] Appl. No.: 70,781

2,392,808 1/1946 Chapman ..317/2 r 3,264,403 8/1966 Erdle ...174/72 133,466,745 9/1969 Stopp ..174/72 B Primary Examiner-L. T. l-lixAttorney-Fishman and Van Kirk 57 ABSTRACT A laminated static chargesuppressing bus which is composed of a strip of insulating material towhich a conducting strip and a plurality of ionizing elements aremounted. The conducting strip is mounted on one side of the insulatingstrip and the plurality of ionizing elements are mounted serially alongthe other side of the insulating strip directly opposite the conductingstrip. The ionizing elements are capacitively coupled to the conductingstrip and contain pointed emitting tips extending beyond the edge of theinsulating strip. When the ionizing elements are excited, the emittingtips establish a corona discharge in gas around the tips for removingstatic charges from paper, plastic webs and sheetlike textile materials.

10 Claims, 4 Drawing Figures PATENTEDMAH 28 m2 INVENTORS MICHAEL F.IOSUE ROBERTE. $A/v0ERs Attorneys LAMINATED STATIC CHARGE SUPPRESSOR ANDMETHOD OF MAKING SAME BACKGROUND OF THE INVENTION l. Field of theInvention This invention relates to the field of static suppressors andis more particularly directed to static suppressors used inmanufacturing paper, plastic webs and other sheetlike textiles.

2. Description of the Prior Art In many manufacturing processes, a webof material is translated over rollers or through wiping elements and inthese processes, the web may acquire a charge of static electricity.

For many operations, it is desirable to have a charge-free web or sheetto facilitate handling of the material and to obviate any possibility ofa static discharge occurring between the web and other structures.Furthermore; it may-be necessary to deliver the finished web material ina charge-free form. In any of the above cases, the removal of a staticcharge may be accomplished by passing the web in close proximity to acharge suppressing device.

There' are already a number of charge suppressing devices available andin use. One such device is composed of a high voltage cable having aplurality of pointed emitter pins projecting laterally along one side ofthe conductor. A high voltage conductor within the cable is coupledcapacitively through insulation to each of the emitter pins. The cableis mounted in a grounded, cylindrical, metallic shell having alongitudinal slot. The emitter pins project from the cable through thelongitudinal slot to a region adjacent the web as the web is transportedpast the pins. By exciting the high voltage conductor with suitable ACpower, the pointed ends of the emitter pins ionize air in the immediatevicinity of the pins in a corona discharge. The ionized air serves as aconductive path and allows static charges to be drained from the webthrough the metallic shell to ground. Thusly, all static charge isremoved from the web.

(A reference to pointed emitting tips or pins is to be interpretedthroughout the specification and claims to include tapered pins or pinshaving small diameter, rounded end surfaces suitable for generating thecorona discharge.)

While the prior art static suppressors are adequate as far as theiroperating capabilities are concerned, the cost of manufacturing theprior art suppressors, particularly a coaxial suppressor, issubstantial. A selected, uniform capacitive coupling between the highvoltage conductor and the emitter pins must be insured and contributesto the manufacturing costs. It is, accordingly, desirable to have astatic suppressor bus which can be manufactured more cheaply than theprior art busses, and without substantial difficulties in controllingthe uniformity of the capacitive coupling in the bus.

SUMMARY OF THE INVENTION In accordance with the present invention, alaminated static charge suppressing bus is formed principally of a basestrip of insulating material, a high voltage conductor and a pluralityof ionizing elements or emitters. The high voltage conductor is also inthe form of a strip and is secured to one side of the insulating basestrip. The plurality of ionizing elements take the form of smallcapacitor plates from which pointed emitters project and are mounted tothe other side of the base strip. The ionizing elements are positioneddirectly opposite the high voltage conductor for optimum capacitivecoupling. Also, the ionizing elements are positioned serially along thebus with the pointed emitters projecting slightly beyond the edge of thebase strip. A layer of insulation is applied to the exposed surfaces ofthe high voltage conductor and the ionizing elements.

Since the novel static charge suppressing bus has a laminatedconstruction, it may be readily manufactured by building up the bus fromthe base strip in a sequence of simple operations. The high voltageconductor is applied to one side of the base strip and the ionizingelements are applied to the opposite side of the strip. To facilitatethe handling and positioning of the plurality of ionizing elements, theelements are stamped from a single strip of material and bridgingportions are retained between adjacent elements so that all of theelements are interconnected. In this fashion the plurality of elementsmay be handled as a single strip while the elements are mounted. Theinterconnections between elements can be removed after the elements arein position. The base strip of insulating material and the externallayers of insulation may initially be an uncured epoxy fiberglass sothatthe finished laminated structure can be held together in a moldedform by the cured epoxy.

BRIEF DESCRIPTION OF THE DRAWINGS The novel laminated static chargesuppressing bus and its method of construction will be described andbetter understood by reference to the following drawings in. which thesame elements bear the same reference numerals throughout the severalfigures.

FIG. 1 is a cross-sectional view of a prior art coaxial staticsuppressing bus mounted within a grounded metal shield for removingstatic charge from a film.

FIG. 2 is a side view of the laminated static charge suppressing bus ofthe present invention with portions of the different laminates removed.

FIG. 3 is a cross-sectional view of the laminated bus as viewed alongthe section line 3-3 in FIG. 2.

FIG. 4 is a side view of two interconnected ionizing elements as theelements appear at an intermediate stage of manufacture.

DESCRIPTION OF THE PREFERRED EMBODIMENTS To more clearly understand theoperation and function of the laminated static suppressor bus of thepresent invention, reference is first made to the prior art staticsuppressors shown in FIG. 1 in a working environment. The laminatedstatic suppressor of the present invention is intended to replace theprior art coaxial suppressors in the same environment.

FIG. 1 shows a web or film F being transported in the directionindicated by the arrow over the coaxial static suppressor, generallydesignated 10, shown in cross section. The film F may be any type offilm such as paper, plastic and other sheetlike textile materials whichare likely to acquire a static charge during manufacturing or otherprocessing. The film F may acquire such charge by frictional contactwith other structures such as rollers, slides and brushes. Static chargeacquired by the film F may interfere with subsequent handling of thefilm due repulsion or attraction caused by the static charge. The chargeitself may interfere with the application of coatings or the wetting ofthe film by liquids in a given manufacturing process. The staticsuppressor might be employed as the last step of a manufacturing processso that the film can be delivered as a finished item without residualstatic charges. The suppressor may simply remove static charges beforethey reach a level which could create a damaging or, possibly,catastrophic discharge between the film and surrounding structure.

The prior art coaxial suppressor 10 is composed basically of a centralhigh voltage conductor 12 and a plurality of ionizing pins 14 withpointed emitting tips 16. The pins 14 are distributed serially along oneside of the suppressor and project radially through an outer layer 18 ofinsulation. Each pin 14 is press-fitted at its inner end in acorresponding ring 20. Both the pins 14 and the rings 20 are metallicelements and are, therefore, electrically conductive. The ring 20 ispositioned coaxially with respect to the high voltage conductor 12 andis separated from the conductor 12 by means of an inner layer 22 ofinsulation. The radial thickness of the layer 22 is selected so that thecapacitive coupling between conductor 12 and ring 20 establishes a highvoltage at the pointed emitting tips 16 of pins 14 and produces a coronadischarge in the vicinity of the tips. The thickness of the layer 22must be sufficient to prevent direct discharges between conductor 12 andlayer 22 and, therefore, varies according to the dielectric constant ofthe insulating material.

The coaxial bus is mounted transversely to the film F within a grounded,metallic sleeve 24 by brackets (not shown). Pins 14 project radiallythrough a longitudinal slot 26 extending along one side of sleeve 24.The plurality of pins 14 and associated rings are positioned seriallyalong the coaxial bus 10. Each set of a pin and ring is electricallyisolated from the other sets. The separation between the pins and thenumber of pins is selected so that static charge across the entiresurface of film F is removed.

In operation, the high voltage conductor 12 is excited by an AC powersource, for example a source providing 80015,000 volts at 60 c.p.s. Thecapacitive coupling of conductor 12 through layer 22 to a ring 20 andpins 14 raises the voltage at the emitting tips to a value which ionizesthe air locally around the tips 16 of pins 14. The ionized air forms aconductive path between the film F and the grounded sleeve 24 so thatstatic charges can be removed from the film F as it translates in closeproximity to the emitting tips 16. The static charge is safely drawn offthe film through the ionized gas and sleeve 24 before the chargeinterferes with or injures the film.

While the prior art coaxial static suppressor busses operate inessentially the same fashion as the laminated suppressor of the presentinvention, the coaxial construction is considerably more costly andutilizes more space while performing the same function. The positioningof several pins with rings at stations serially along the coaxialconductor and the formation of the coaxial package require a moresophisticated manufacturing process than that permitted by a laminatedconstruction. The laminated structure, taking a planar form, is wellsuited to designing and controlling capacitive coupling between the highvoltage conductor and emitters and occupies considerably less spacewhile performing the same static suppressing function within adischarging envelope such as sleeve 24 in FIG. 1.

Accordingly, the novel laminated static charge suppressing bus,generally designated 30, is shown in FIG. 2 with portions of the severallaminates removed to expose the internal construction. The completelaminated structure is shown in crosssection in FIG. 3.

The intermediate layer of the laminated structure is a strip 32 ofinsulating material which forms a base of limited stiffness upon whichthe other laminates are built. The base strip 32 may be an epoxyfiberglass having a thickness primarily established to provideinsulation between the high voltage conductor 34 and the plurality ofionizing tip plates 36. The spanwise stiffness of the laminate structureis controlled principally by the thickness of the base strip 32 and theconductor 34. lnterposed between the base strip 32 and the high voltageconductor 34 is another layer 38 of epoxy fiberglass which is used inconjunction with the external layer of fiberglass 40 to mount the highvoltage conductor 34 to the base strip 32. The layer 38 is optional ormay simply be a part of the base strip 32. The conductor 34 is a stripof highly conductive material, such as brass or copper, and extendscontinuously along one side of strip 32. Dimensionally, the conductor 34has a width which is less than that of strip 32 to provide an apronalong the one edge of strip 32 for mounting the laminated bus in closeproximity to a film as the coaxial bus 10 is shown in FIG. 1. Thelaminated construction is completed by a second insulating layer 42which covers the exposed surfaces of the tip plates 36. a

The tip plates 36 have a planar configuration with the emitters 44projecting from one side of the rectangular body portion of the plate36. The projecting ends 46 of emitters 44 are pointed for ionizing gasin the same manner as the pointed tips 16 of pins 14 in the prior artsuppressor 10 shown in FIG. 1. Plate 36 is positioned and oriented onthe one side of base strip 32 so that the plate is directly opposite thehigh voltage conductor 34. The width of the conductor 34 and theparallel dimension of the plate are substantially equal, therefore, astructure resembling a conventional flat capacitor is formed betweenconductor 34 and each of the plates 36. The thickness of base strip 32and the additional layer 38 determine the capacitance between plate 36and conductor 34. The significant considerations in this regard are theseparation between the plates and conductor and the dielectric constantof the intervening material since these principal factors determine thebreakdown voltage between the conductor 34 and plates 36. The voltagesrequired to generate a corona ring around the emitter tips 46 must becomparatively high, in the vicinity of 800- 15,000 volts; therefore, thethickness of the base strip 32 and other intervening layers must beselected to insure adequate electrical isolation without dischargeswhich could lead to catastrophic failure of the suppressing bus.

The laminated bus 30 can be mounted in a number of ways. As shown in FIG. 2, a plurality of apertures 50 are distributed along the apron atthe upper edge of base strip 32. The apertures 50 also extend throughlayers 38, 40 and 42 of insulation so that mounting screws 52 may beinserted through the bus and associated mounting brackets. If themounting apertures 50 are close to conductor 34, the conductor mayinclude a cutout 54 in the contiguous conductor section to provideadequate electrical isolation.

At one end, conductor 34 is joined with a connector 56 for connectingthe bus 30 to a suitable source of AC power. The connector may be eithercrimped, clamped or soldered to the connector '44 to provide a lowresistance, low capacitance junction for the high voltage AC power.

One of the significant advantages of the laminated suppressor structureis the lower cost of construction due principally to the fact that amore simplified assembly procedure can be followed. Basically, each ofthe elements are individual laminates which need only to be sandwichedin a unified structure. In manufacturing the coaxial constructions ofthe prior art, the locating and assembling of the various components ismore difficult and must be more accurately controlled to preserveproduct quality. It is appropriate, however, to examine preferredmethods by which the laminated suppressing bars of the present inventionare manufactured.

Initially the base strip 32 of epoxy fiberglass is placed inside-by-side relationship with the strip 34 of conductive material withthe aid of the fiberglass insulating layers 38 and 40. The epoxyfiberglass of both strip 32 and layers 38 and 40 can be easily moldedand formed against conductor 34 when the epoxy is in the uncured stage,commonly known as the B stage. The conductive strip 34 is positionedgenerally intermediate the lateral edges of the base strip 32 with asufficient apron at one side of strip 32 to accommodate the mountingapertures 50. The apertures may be formed during the molding of thefiberglass with the conductor 34 since the cutouts 54 in the conductormust correspond with the apertures. Of course, it is feasible toinsulate the mounting screws 52 from the conductive strip 34 in mountingholes lying wholly within conductor 34 where an ample conductor crosssection is provided.

The next step in the manufacturing process for suppressing bar 30 is themounting of the plurality of tip plates 36 to the side of the base strip32 opposite the conductor 34. As will be understood from the abovedescription of the operation of the suppressor bus 30, tip plates 36must be located at selected stations along base strip 32 and inpositions on the base strip 32 which are directly opposite the conductor34 to provide the most efficient capacitive coupling between strip 34and the plates 36. Furthermore, the precise positioning of plates 36 isalso demanded by the fact that the pointed emitting tips 46 of eachplate 36 must be located in substantially the same plane so that theseparations between the several emitting tips and a film to bedischarged are equal when bus 30 is mounted in close proximity to afilm. It will be immediately recognized that the individual positioningof several plates with the emitters 44 precisely located could be atime-consuming and difficult step of the manufacturing process.Accordingly, the tip plates 36 with the integral emitters 44 are formedfrom a single strip of conductive material, such as stainless steel, by

stamping all plates simultaneously with bridging portionsinterconnecting the plates. As seen from FIG. 4 where the'plates areshown at reduced scale, the bridging portions 60 extend between theemitters 44 of adjacent plates. A die for stamping such plates can bereadily constructed and is capable of producing a plurality ofinterconnected plates rapidly. Of course, it may be equally desirable toemploy a chemical etching process to form the interconnected plates.

The mounting of the plurality of plates interconnected through theemitters 44 can be readily accomplished by locating the interconnectedplates on the base strip 32 in a position directly oppositeconductor 34.Separation and orientation of the plates are kept uniform by thebridging portions 60.

Once the plates have been properly located, the external layer 42 ofepoxy fiberglass is overlaid on the exposed surfaces preferredembodiment, numerous changes to thesp'ecific structure are possiblewithout losing the essential benefits of the laminated construction.The'laminated bus and its method of manufacture have, accordingly, beendescribed byway of of the plates. Theentire laminated structure is thenplaced in a pressurized mold and cured by applying heat and pressure fora prescribed period of time to set the epoxy resin inthe fiberglass. Itis advantageous to maintain the interconnecting portions'60 between theseveral plates 36 during thecuring process so that the alignment andpositioning of the plates is not disturbed before the epoxy is set.

' The removal of the bridging portions 60 after curing is accomplishedby cutting the emitters along the dotted line indicated in H6. 4 to formthe pointed tips 46 seen in FIG. 2. A

separate cutting die may be employed to cut the pointed emitters or theemitters may be partially severed from the bridging portions 60 duringthe initial stamping of the plates to weaken the union of the emittersand bridging portions at the dotted linesin FIG. 4. The severance canthen be completed after the fiberglass has cured. Since theinterconnecting portions 60 preserve the spacing and orientation of theplates 36 during the curing process, positioning of the plates will'beuniform.

' finished laminated suppressor bus occupies considerably less spacewhile performing the same function as the prior art coaxial suppressorbusses.

It will be understood by those skilled in the art that numerousmodifications and substitutions can be made in the structure and themanufacture of the novel laminated suppressor bus without departing fromthe spirit of the invention-For example, while an epoxy fiberglass hasbeen described as the base material forming the insulation betweenconductor'34 and plates 36, other fiber-reinforced or plastic materialsused as substrates for electrical components can be utilized withequally satisfactory results. The materials from which the conductors 34and plates 36 are formed may also be changed so long as the electricalcharacteristics of the materials are preservedJt is also obvious thatthe order in which the strips 32, 34 and the interconnected plates 36are assembled prior to curing may be interchanged. In certain cases itmay be desiraillustration rather than limitation. I

What is claimed is: 1

1; A laminated static charge suppressing bus comprising: a base strip ofinsulating material 1 having a preselected thickness between oppositesides of the strip to provide a given capacitance between the sides ofthe strip;

a continuous strip of conductive material mounted at one side of thebase strip; and v a plurality of ionizing elements mounted at the otherside of the base strip, the ionizing elements each being formed from aconductive material and having a pointed tip projecting therefrom. I ,2.The laminated suppressing bus of claim 1 wherein: the plurality ofionizing elements are electrically isolated from each other. f 3. Thelaminated suppressing bus of claim 1 wherein: the plurality .of ionizingelements are distributed at intervals along the other'side of the basestrip. v 4. The laminated'suppressing bus of claim 1 wherein: theionizing elements areplates positioned on theother side of the basestrip parallel to the continuous strip of conductive materialwhereby theplates and continuous strip may be capacitively coupled through the basestrip. 5. The laminated suppressing bus-of claim 4 wherein the plateshave a rectangular configuration with one side correspondingdimensionally to the width of the continuous conductive strip.

6. The laminated suppressing bus of claim 4 wherein: the pointed tipsproject from the periphery of the plates. 7. The laminated suppressingbus of claim 1 wherein: the ionizing elements are distributedperiodically along the other side of the base strip; and the pointedtips project from the elements parallel to the other side and beyond anedge of the other side. 8. The laminated suppressing bus of claim 1further includmg: a' layer of electrical insulating material coveringthe exposed surfaces of the continuousstrip of conductive material.9'..The laminated suppressing busof claim 8 including still further:

a layer of electrical insulating material covering the exposed surfacesof each ionizing element. 1 0. The laminated structure of claim 1wherein: I I the ionizing elements are planar elements mounted on thebase strip directly opposite. the continuous, conductive strip wherebythe conductive strip may be capacitively coupled to each of the elementsthrough the base strip.

1. A laminated static charge suppressing bus comprising: a base strip ofinsulating material having a preselected thickness between oppositesides of the strip to provide a given capacitance between the sides ofthe strip; a continuous strip of conductive material mounted at one sideof the base strip; and a plurality of ionizing elements mounted at theother side of the base strip, the ionizing elements each being formedfrom a conductive material and having a pointed tip projectingtherefrom.
 2. The laminated suppressing bus of claim 1 wherein: theplurality of ionizing elements are electrically isolated from eachother.
 3. The laminated suppressing bus of claim 1 wherein: theplurality of ionizing elements are distributed at intervals along theother side of the base strip.
 4. The laminated suppressing bus of claim1 wherein: the ionizing elements are plates positioned on the other sideof the base strip parallel to the continuous strip of conductivematerial whereby the plates and continuous strip may be capacitivelycoupled through the base strip.
 5. The laminated suppressing bus ofclaim 4 wherein the plates have a rectangular configuration with oneside corresponding dimensionally to the width of the continuousconductive strip.
 6. The laminated suppressing bus of claim 4 wherein:the pointed tips project from the periphery of the plates.
 7. Thelaminated suppressing bus of claim 1 wherein: the ionizing elements aredistributed periodically along the other side of the base strip; and thepointed tips project from the elements parallel to the other side andbeyond an edge of the other side.
 8. The laminated suppressing bus ofclaim 1 further includinG: a layer of electrical insulating materialcovering the exposed surfaces of the continuous strip of conductivematerial.
 9. The laminated suppressing bus of claim 8 including stillfurther: a layer of electrical insulating material covering the exposedsurfaces of each ionizing element.
 10. The laminated structure of claim1 wherein: the ionizing elements are planar elements mounted on the basestrip directly opposite the continuous, conductive strip whereby theconductive strip may be capacitively coupled to each of the elementsthrough the base strip.